The aim of this proposal is to evaluate the biologic effects of laser welding on vascular healing. The hypotheses being tested are that using laser tissue welding for vascular repairs and anastomoses will 1) expedite surgical procedures by alleviating the need for suture techniques and instrumentation; 2) diminish long-term complications related to tissue trauma; 3) promote the maintenance of normal arterial properties such as compliance; and 4) possibly prevent neointimal hyperplasia, atherosclerotic degeneration, and calcification of the vessel. These hypotheses will be tested by experiments designed to study the histologic, biochemical, and mechanical properties of primary repair of venotomies and arteriotomies formed by laser welding using CO2, argon, and Nd:YAG lasers, compared to controls using conventional suture techniques. Subsequent experiments will examine the same experimental parameters in laser and control venous and arterial anastomoses. Additional experiments will explore the feasibility of forming artery-vein and artery-vascular prosthetic laser anastomoses. An aim of the prosthetic anastomotic experiments is to explore and maximize the ability to form tissue-prosthetic bonding using commercially available materials and experimental blood compatible polymers. Preliminary experiments in our laboratory have demonstrated the ability to repair venotomies using CO2 and Nd:YAG lasers, and to repair arteriotomies using argon and Nd:YAG lasers. Additional experiments have evaluated the biochemical effects of laser-tissue interactions, suggesting the ability to selectively modulate the collagen production in healing lesions using the laser. The methodology described in this proposal has enabled us to accurately quantitate and reproduce experimental observations. Each laser appears to have specific capabilities, thus, longer-term studies of laser welds compared with controls fashioned by conventional suture techniques are required to determine the rate and character of healing and to assess the laser effects on specific tissue elements and adjacent tissues. Development of an expedient non-suture technique for repairing venous and arterial lesions and making anastomoses would be cost and time effective, reduce the technical difficulties of procedures and improve the quality of patient care.